Silurian conodont-based correlations between Gotland (Sweden) and Saaremaa (Estonia)

Correlations between the Silurian successions of Gotland and the East Baltic are based on the narrowest stratigraphic units that can be distinguished in both areas. In order further to increase precision, true ends of ranges in measured sections have been used instead of ‘pooled’ formational faunas, where outcrops and collections permit. Some previous correlations are confirmed. In other cases, there are considerable changes both in levels of correlation and in precision. The major differences are found mostly when one or more of the major gaps have remained unrecognized and stratigraphic units therefore have been extended and translated upwards or downwards. At least some of these gaps decrease in magnitude southwards in Estonia. Gaps at these levels are also noted on Gotland, although they are small and probably do not extend across the island. The patterns through time of deposition (during secundo episodes) and gaps (during primo episodes) agree very well with what can be predicted from a model of oceanic and climatic cyclicity.